Examples of known cutting tools used for carrying out cut processing on a work material such as a metal include a cutting insert described in Japanese Unexamined Patent Application Publication No. 2012-45634A (Patent Document 1), and a throw-away tip described in Japanese Unexamined Patent Application Publication No. H11-197909A (Patent Document 2). The tip described in Patent Document 2 includes a cutting edge having a linear shape and located near a top surface having a rhombic shape, and a nose cutting edge located in a corner portion of the top surface. Further, a rake angle of a section along the cutting edge of a rake face on the top surface is constant while a rake angle of a section along the nose cutting edge varies.
While the rake angle is increased in order to decrease a cutting resistance, a thickness of a tip (cutting insert) between side surfaces and the rake face decreases in such a case. Chips cut by a first cutting edge of a pair of cutting edges having a linear shape and sandwiching the nose cutting edge (corner cutting edge) pass over a rake face disposed along this first cutting edge, and then advance towards a second cutting edge of the pair of cutting edges having a linear shape.
The chips that have advanced towards the second cutting edge collide with a rake face disposed along the second cutting edge and curl. When the rake angle is large and the cutting insert is thin at this time, the collision of chips at a high feed rate or the like may cause the rake face disposed along the second cutting edge to wear and become damaged.
In light of the above-described problems, the present embodiment provides a cutting insert capable of decreasing damage to a rake face and carrying out favorable cut processing.